The present invention concerns a method of joining two reinforced thermoplastic material tubes having the same diameter.
Pipes for transporting fluids in cities are made from tubes of small diameter, on the order of 80 to 200 mm. The tubes are often made from reinforced thermoplastic material.
To assure the continuity of the pipes, two ends of such reinforced thermoplastic material tubes must often be joined in a sealed manner at an installation site.
It is well known in the art to use metal connectors to connect two tube ends in order to guarantee that the resulting pipe has the same resistance to external stresses in the area of the joint and in the main part of the tubes.
These metal connectors are weak in terms of axial loads and do not assure effective locking of the joint. A tube end often separates from the connector when the pipe is pressurized.
The object of the invention is to provide a method of joining two reinforced thermoplastic material tubes which is simple to perform and guarantees satisfactory strength of the resulting pipe in the region of the connection as well as effective locking, and prevents any separation in response to axial loads.
To this end, the invention consists in a method of joining two reinforced thermoplastic material tubes having the same diameter. Ends of the two tubes are first butt welded along a peripheral weld and, after forming the weld, a reinforced thermoplastic material outer jacket is fitted over most of the length of the peripheral weld. The reinforced outer jacket extends on either side of the weld over end sections of the two tubes. The outer jacket is heated and pressed radially until the outer jacket and the end sections of the two tubes interpenetrate.
Particular embodiments of the method have one or more of the following features:
radial pressure is applied to the outer jacket until reinforcing structures reinforcing the two tubes and the outer jacket come into contact upon interpenetration of the outer jacket and the end sections of the two tubes;
the outer jacket comprises a tubular cylinder defining a closed contour enveloping the end sections of the tubes;
the outer jacket comprises a longitudinally split cylinder enveloping the end sections of the tubes;
the circumferential length of the outer jacket is such that the outer jacket defines a closed contour around the two tubes after interpenetration of the jacket and the end sections of the two tubes;
the outer jacket includes composite threads including continuous glass filaments and continuous organic thermoplastic material filaments, which filaments are adapted to form a web;
the organic thermoplastic material is polyethylene;
the composite threads of continuous glass filaments and continuous organic thermoplastic material filaments crossxe2x80x94cross;
the composite threads are wound helically and define angles of substantially +55xc2x0 or xe2x88x9255xc2x0 with the axis of the outer jacket;
the composite threads define angles of substantially 0xc2x0 and 90xc2x0 with the axis of the outer jacket;
the continuous glass filaments and the continuous organic thermoplastic material filaments are woven;
the axial length of the outer jacket is in the range from 0.5 times to 3 times the diameter of the tubes to be joined;
the ends of the tubes are butt welded without filler material, in particular by mirror welding; and
a protective sleeve is fitted over the entire surface of the outer jacket after it is applied to the tubes.